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Speech decoder that detects stationary noise signal regions

Inactive Publication Date: 2009-01-13
PANASONIC CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007]It is therefore an object of the present invention to provide a speech decoding apparatus that correctly identifies the stationary noise signal period and decodes speech signals. To be more specific, it is an object of the present invention to provide a speech decoding apparatus and speech decoding method for identifying the speech period and the non-speech period, distinguishing periodic stationary signals from stationary noise signals (e.g. white noise) using the pitch period and adaptive code gain, and correctly identifying the stationary noise signal period.
[0008]To achieve the object, the present invention proposes an apparatus and method for tentatively evaluating the properties of stationary noise of a decoded signal, determining whether the current processing unit represents a stationary noise period based on the tentatively evaluated stationary noise properties and the periodicity of the decoded signal, separating the decoded signal containing stationary speech signal such as stationary vowels from stationary noise, and correctly identifying the stationary noise period.

Problems solved by technology

However, with the prior-art speech decoding apparatus, it is difficult to distinguish signals that are stationary but are not noisy (e.g. stationary vowels) from stationary noise and identify a stationary noise period.

Method used

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  • Speech decoder that detects stationary noise signal regions

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first embodiment

[0022]FIG. 1 illustrates a configuration of a stationary noise period identifying apparatus according to the first embodiment of the present invention.

[0023]Given a digital signal input, an encoder (not shown) first performs an analysis and quantization of Linear Prediction Coefficients (LPC), pitch search, fixed codebook search and gain codebook search, and then transmits the LPC code (L), pitch period (A), fixed codebook index (F) and gain codebook index (G).

[0024]A code receiving apparatus 100 receives the encoded signal transmitted from the encoder, and separates the code L representing the LPC, a code A representing an adaptive code vector, code G representing gain information and code F representing a fixed code vector, from the received encoded signal. The code L, code A, code G and code F are output to a speech decoding apparatus 101. TO be more specific, the code L is output to an LPC decoder 110, code A is output to an adaptive codebook 111, code G is output to a gain code...

second embodiment

[0088]FIG. 5 illustrates the configuration of a stationary noise post-processing apparatus according to the second embodiment of the present invention. In FIG. 5, the same parts as in FIG. 1 are assigned the same reference numerals as in FIG. 1, and specific descriptions thereof are omitted.

[0089]A stationary noise post-processing apparatus 200 is comprised of a noise generator 201, adder 202 and scaling section 203. In stationary noise post-processing apparatus 200, adder 202 adds a pseudo stationary noise signal generated in noise generator 201 and the post-filter output signal from speech decoding apparatus 101, scaling section 203 adjusts the power of the post-filter output signal after the addition by performing scaling processing, and the resulting post-filter output signal becomes outputs of stationary noise post-processing apparatus 200.

[0090]Noise generator 201 is comprised of an excitation generator 210, synthesis filter 211, LSP / LPC converter 212, multiplier 213, multipli...

third embodiment

[0105]FIG. 6 illustrates a configuration of a stationary noise post-processing apparatus according to the third embodiment of the present invention. In FIG. 6, the same parts as in FIG. 5 are assigned the same reference numerals as in FIG. 5, and specific descriptions thereof are omitted.

[0106]In addition to the configuration of stationary noise post-processing apparatus 200 shown in FIG. 2, the apparatus in this embodiment further comprises memories for storing parameters required in noise signal generation and scaling upon frame erasure, a frame erasure concealment processing controller for controlling the memories, and switches used in frame erasure concealment processing.

[0107]A stationary noise post-processing apparatus 300 is comprised of a noise generator 301, adder 202, scaling section 303 and frame loss compensation processing controller 304.

[0108]Noise generator 301 has a configuration that adds to the configuration of noise generator 201 shown in FIG. 5, memories 310 and ...

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Abstract

A first determiner 121 tentatively determines whether the current processing unit represents a stationary noise period, based on stationary properties of a decoded signal. Based on the tentative determination result and a determination result of the periodicity of the decoded signal, a second determiner 124 determines whether the current processing unit represents a stationary noise period, thereby distinguishing a decoded signal including a stationary speech signal such as a stationary vowel from stationary noise and correctly identifying the stationary noise period.

Description

TECHNICAL FIELD[0001]The present invention relates to a speech decoding apparatus that decodes speech signals encoded at low bit rates in a mobile communication system and packet communication system (e.g. internet communication system). More particularly, the present invention relates to a CELP (Code Excited Linear Prediction) speech decoding apparatus that divides speech signals into the spectrum envelope component and the residual component.BACKGROUND ART[0002]In mobile communications, packet communications (e.g., internet communications) or speech storage, speech coding apparatuses are used for compressing speech information by using efficient encoding. This is for effective use of the capacity of transmission layer resources like radio frequencies or the capacity of storage media. Among those, systems based on the CELP (Code Excited Linear Prediction) system are carried into practice widely at medium and low bit rates. Techniques of CELP are described in M. R. Schroeder and B. ...

Claims

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Application Information

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IPC IPC(8): G10L11/06G10L15/00G10L19/12G10L21/00G10L25/84G10L19/012G10L19/04G10L25/78G10L25/90
CPCG10L19/012G10L19/04G10L25/78G10L25/90G10L19/12G10L25/84
Inventor EHARA, HIROYUKIYASUNAGA, KAZUTOSHIMANO, KAZUNORIHIWASAKI, YUSUKE
Owner PANASONIC CORP
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